A significant increase of percentage of α2,3-sialylated PSA in the group of high-risk PCa patients (26.8–61.4%) compared with the other three groups, intermediate-risk PCa (12.7–35.5%; p < 0.001), low-risk PCa (12.3–29.9%; p = 0.006), and BPH (10.9–33.5%; p < 0.001) was shown. The gene discussed is KLK3; the disease is benign prostatic hyperplasia.